Genetics - Section 1 Multiple Questions and Answers.




11.Which structural feature is found in the single-stranded DNA molecule?
A. It can have a negatively-charged backbone composed of nitrogenous bases.
B. Each 3’,5’-phosphodiester bond will contain one phosphate group linking two deoxyribose sugars.
C. It can have one end with a 5’-phosphate group while the other end has a 2’-hydroxyl group.
D. Each purine and pyrimidine will be paired with a complementary base.

12.Which is a possible sequence and structure for this DNA molecule?
A. If the single-stranded molecule has the sequence 5’-(ATGC)10, then its double- stranded form could assume a Z-DNA structure
B. If the single-stranded molecule has the sequence 5’-(GATC)10, then its double-stranded form could assume an H-DNA structure
C. If the single-stranded molecule has the sequence 5’-(CTGA)10, then its double-stranded form could assume a hairpin structure.
D. If the single-stranded molecule has the sequence 5’-(TGAC)10, then its double-stranded form could assume a cruciform structure.

13.Which characteristic does this double-stranded molecule have when it forms a B- DNA structure?
A. The two strands will have parallel orientation and identical sequences.
B. The helix will be right-handed with 12 base-pairs per turn
C. Every base-pair will contain one purine and one pyrimidine.
D. There are both covalent and non-covalent bonds between the two chains.

14.Which force can stabilize a DNA double-helix?
A. Hydrophobic bases are found in the interior of the helix where each base- pair is stabilized by the same number of hydrogen bonds
B. Hydrophilic sugar-phosphate groups are found on the exterior of the helix where they can interact with water.
C. Non-covalent N-glycosidic bonds can form between nitrogenous bases in opposite strands in the helix
D. Covalent base-stacking interactions can occur between adjacent bases within the same strand in the helix.

15.Which of the following double-stranded DNA molecules would denature at a lower temperature than the 40 base-pair double-stranded molecule described above?
A. a 40 base-pair molecule in which 25% of the bases are adenines
B. a 30 base-pair molecule in which 40% of the bases are guanines
C. a 20 base-pair molecule in which 10% of the bases are thymines
D. a 10 base-pair molecule in which 20 % of the bases are cytosines

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